1. Field of the Invention
The present invention relates to a color conversion coefficient calculation apparatus, a computer readable recording medium for recording a color conversion coefficient calculation program, and a color conversion coefficient calculation method for calculating a color conversion coefficient to convert a first color signal made up of a plurality of chrominance signals into a second color signal made up of a plurality of chrominance signals.
2. Description of the Related Art
It is known that in an image pickup apparatus such as a digital camera and the like, color reproduction may vary when the same subject is photographed in different environments. However, in reality, color reproduction may vary, without being limited to such a case, even when the same subject is photographed in the same environment.
While an image pickup apparatus is configured to use, for example, an image pickup device equipped with a color filter to pickup images, such an image pickup device equipped with a color filter has different characteristics relating to color reproduction, such as spectral characteristics, etc. depending on the type thereof. Moreover, even among image pickup devices of the same type, the characteristics thereof may differ among individuals depending on the materials and manufacturing processes thereof, and aging degradation, etc. Therefore, due to such difference in characteristics, the color reproduction in individual image pickup apparatus will vary as well. Color reproduction is regarded as one of important factors particularly in the medical field, and variation in color reproduction may possibly disturb diagnostics.
To solve such a problem, various color correction technologies have been developed in recent years; for example, a technology to perform color correction by using a fixed color correction coefficient which is not dependent on individual image pickup apparatuses is proposed. However, this technology is not yet able to cope with the differences in characteristics among individuals of an image pickup apparatus.
For example, Japanese Patent Application Laid-Open Publication No. 2001-358960 describes a technology to derive a color correction coefficient for performing a linear conversion of a signal characterized by a first spectral sensitivity distribution into a signal characterized by a second spectral sensitivity distribution based on the first spectral sensitivity distribution and the second spectral sensitivity distribution. Applying this technology to each individual image pickup apparatus allows for the derivation of an optimum color correction coefficient to absorb the difference between two spectral sensitivity distributions.
Moreover, Japanese Patent Application Laid-Open Publication No. 2005-117524 describes a technology by which a color chart is photographed for each of plural image pickup apparatuses and a color correction coefficient is derived so that image data agree with one another among photographed color charts.